U.S. Pat. No. 3,143,817 (Paulson 1964) discloses a post with an integral hammer and anvil that enables a ground piercing member forming part of the post to be hammered into the ground or hammered out of the ground. The ground piercing member is elongate and has a ground piercing end and an anvil end. An anvil is positioned at the anvil end of the ground piercing member. This anvil has a first striking face and a second striking face. The first striking face is opposed to the second striking face. A tubular housing is provided a first end, a second end, and an interior cavity. The anvil is positioned within the interior cavity of the housing with the ground piercing member extending through the second end of the housing. A first hammer is positioned at the first end of the housing. Relative movement of the ground piercing member and the housing brings the first hammer into contact with the first striking face of the anvil to drive the ground piercing end of the ground piercing member into the ground. A second hammer is positioned at the second end of the housing. Relative movement of the ground piercing member and the housing brings the second hammer into contact with the second striking face of the anvil to remove the ground piercing end of the ground piercing member from the ground.
When a post similar to that disclosed in the Paulson reference is used to tether horses, problems arise. In response to a force exerted by the horse, the post tends to telescopically extend. Once the post is in a telescopically extended position, the horse is able to exert sufficient leverage to either pull the post out of the ground or bend ground piercing member.